Transfer pattern printing is a technique involving a continuous transfer of a pre-printed pattern from a pattern-carrying web to the textile web, where the two webs are continuously brought into contact with one another in a transfer region which is frequently in the form of one or more pairs of pressure rollers.
Transfer pattern printing is a technique which has been used for a long time and which has been commercially interesting since the 19-fifties, especially in form of sublimation transfer printing for use in connection with printing on textile webs of synthetic fibres. Compared to a direct textile printing, the latter sublimation transfer printing ensures the advantage that it is possible very quickly to adapt the production to other patterns in such a manner that it is only necessary to keep a stock of the designs presenting an actual demand. The direct textile printing necessitates, however, in practice often the production of rather large stocks of the individual designs in order to maintain the costs per printed unit of length of the textile web at a reasonable level.
Another advantage obtained by the transfer pattern printing is found in the fact that it is possible to obtain a rather sharp and finely detailed transfer of the patterns, said patterns in advance being printed by means of suitable dyes and with the required fineness and sharpness on a suitable pattern-carrying web.
As a result of the above, the transfer pattern printing has gradually become highly interesting, and various types of the technique has been described in several publications within the patent literature.
U.S. Pat. No. 4,057,864 describes a machine which according to the preamble of claim 1 is to be used for wet transfer pattern printing, and where the pattern-carrying web and the textile web held together one on top of the other are moved about the centre roller and kept in contact therewith by means of an endless belt guided around a portion of the periphery of said centre roller. Some pressure rollers along the periphery of the centre roller provide local compressions of the pattern-carrying web and the textile web.
The transfer pattern printing and other types of roller processes are encumbered with the general problem of obtaining a uniform, linear pressure in the entire length of said rollers, i.e. in the entire width of the textile web, said width often being several meters. This problem is caused by the rollers of one pair of rollers exclusively being supported at the ends. Thus both rollers curve away from one another in the middle due to the pressure, which results in a less linear pressure in the middle. In turn the latter causes a non-uniform transfer of the printed pattern from the pattern-carrying web to the textile web, said transfer often being insufficient in the middle. This problem grows along with an increase of the length of the rollers used and along with an increase of the linear pressure required.
DK-PS No. 169,135 discloses a process for transfer pattern printing of a textile web between pairs of rollers under such a high pressure that the transfer of the pattern from the pattern-carrying web to the textile web can be carried out without the use of heat. The above problem of obtaining a uniform linear pressure applies in particular to this process because a linear pressure of up to 50 kg/cm is used by this process.
Previously, attempts have been made at solving this problem by means of particular pressure rollers where the interior of said roller is subjected to a radially outward pressure by means of a hydraulic fluid in such a manner that the surface of said roller is sufficiently deformed so as to ensure a uniform linear pressure in the entire length of said roller. A system using such rollers is, however, encumbered with the drawback that it is very expensive to produce because it requires a complete hydraulic system with pumps, reservoirs, hydraulic pipes and complicated gaskets between the mutually movable parts.